1. Field of the Invention
The present invention relates to a differential, and more particularly, to a limited slip differential.
2. Discussion of the Related Art
Conventional differentials permit one output shaft to rotate at a different speed relative to the other output shaft. A limited slip coupling may be provided in the differential to prevent this relative rotation under certain conditions. Typically, this coupling employs a mechanical coupling that locks the differential only under a single torque or speed condition.
When a conventional limited slip differential (LSD) is employed in a vehicle driveline, for example, at least two different conditions are desired in which the differential will lock. That is, a high locking factor may be desired to initiate movement of the vehicle. However, a low locking factor is desired during other maneuvers, such as sharp turns at low speed, high speed driving, or at the limits of traction. Unfortunately, due to the mechanical nature of these conventional LSDs, only one of these conditions may be met. For example, an LSD designed to have a high lock-up value will impart a drag during sharp turning maneuvers at low speed.
Accordingly, the present invention is directed to a differential that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide a differential that can accommodate a variety of torque and speed conditions.
Another object of the present invention is to provide a differential capable of operating with a high lock-up and as an open differential.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, the differential includes: a driving member; a first driven member; a second driven member; and a coupling between the driving member and each of the driven members, the coupling includes: an input member connected to one of the driving member, the first driven member and the second driven member; an output member connected to another one of the first driven member and the second driven member, wherein there is a first space between the output member and the input member; a magneto-rheological fluid located in the space; and at least one electromagnet proximate said space.
In another aspect, a variable limited slip differential includes: a driving member; a first driven member perpendicular to the driving member; a second driven member perpendicular to the driving member; a coupling between the driving member and each of the driven members, the coupling includes: a differential coupling; and a variable coupling parallel to the differential coupling, wherein the variable coupling comprises: an input member connected to one of the driving member, the first driven member and the second driven member; an output member connected to another one of the first driven member and the second driven member, wherein there is a space between the output member and the input member; a magneto-rheological fluid located in the first space; and at least one electromagnet proximate the space.
In a further aspect, a method for controlling a differential including a first member and a second member rotatably mounted in a housing, the method includes: sensing an initial throttle position; determining if the initial throttle position is greater than a first value; sensing a speed at each of the first member and the second member if the initial throttle position is greater than the first value; determining if the difference in magnitude between the sensed speeds is greater than a second value; energizing an electromagnet if the speed difference is greater than the second value; and subjecting a magneto-rheological fluid to the magnetic field created by energizing the electromagnet.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.